By way of example, a direct radiation converter is known from DE 10 2006 046 314 A1. This direct radiation converter has a direct conversion layer produced from a material which can convert radiation into electric charge. AlSb, CdS, CdTe, CdZnTe, GaAs, Ge and Se are mentioned as suitable materials.
X-ray detectors, which have an X-ray conversion layer or a scintillation layer which first of all converts incident X-ray radiation into visible light which can be detected using photodiodes, have to be distinguished in principle from direct radiation converters. By way of example, such an X-ray detector is known from DE 10 2005 055 176 A1 and designed as a flat-panel detector.
The selection of a suitable temperature range can in general be significant during the operation of radiation detection apparatuses. DE 101 35 288 B4, relating to a detector module for an X-ray computed tomography scanner, mentions for a sensor array a temperature range from 30° C. to 35° C. which is set by means of a heating element. Tempering an X-ray detector by means of cooling air is disclosed in, for example, DE 10 2006 025 764 B4.
In the case of direct conversion gamma or X-ray detectors, nonlinear relationships which cannot be ignored can occur between the radiation incident on the detector and the generated electric signal, particularly at high radiation densities. Such nonlinear relationships can be traced back to intrinsic impurities in the detector material: fixed charges bound to such impurities intercept the charge carriers generated by the radiation, with the charges being able to recombine therewith. This reduction in the electric field, based on capturing moveable charge carriers and suggesting a significantly lower intensity of the radiation, is referred to as polarization. The polarization is equivalent to forming a space charge in the detector material which hinders charge carrier mobility. Due to the polarization effect, direct radiation converters are subject to severe restrictions with respect to the maximum detectable radiation density.